Global warming might not fuel more intense hurricanes in the Atlantic after all. Despite increasing ocean temperatures that feed the monstrous storms, climate change may also be ramping up the winds that choke off a hurricane’s development, a new study claims.
“The environmental changes here do not suggest a strong increase in tropical Atlantic hurricane activity during the 21st century,” said study team member Brian Soden of the University of Miami.
Hurricanes form as storms shoot off the coast of Africa and pull energy from the warm, moist air over the oceans. As the hurricane intensifies, it begins to rotate. But when winds vary in speed and direction at different heights in the atmosphere, a phenomenon known as wind shear, they prevent the organization of the storm’s circulation, stopping its development or intensification.
Other studies have found that global warming will increase ocean temperatures over the coming century, fueling more intense hurricanes, but this study is the first to suggest that wind shear may also increase and counteract the effects of ocean warming.
“Wind shear is one of the dominant controls to hurricane activity, and the models project substantial increases in the Atlantic,” said study leader Gabriel Vecchi of the National Oceanic and Atmospheric Administration. “Based on historical relationships, the impact on hurricane activity of the projected shear change could be as large—and in the opposite sense—as that of the warming oceans.”
Kevin Trenberth, a climate scientist with the National Center for Atmospheric Research who was not affiliated with the study, pointed out that the model predictions in the new study were averaged. For a given four-year period, for instance, three years could yield suppressed hurricane development, while the fourth could turn out like 2005 (the season that generated Hurricane Katrina), he said.
The models used in the study, detailed in the April 18 issue of the journal Geophysical Research Letters, did show that global warming could lead to a more favorable environment for hurricanes to develop in other regions, including the western tropical Pacific.
“This study does not, in any way, undermine the widespread consensus in the scientific community about the reality of global warming,” Soden said. “In fact, the wind shear changes are driven by global warming.”